code: def test_is_singleton():
      x = Features()
      y = Features()
      assert x is y
  
file_path: mxnet/tests/python/unittest/test_runtime.py
imports: import mxnet
  import sys
  from mxnet.runtime import *
  from mxnet.base import MXNetError
  import pytest
label_desc: Use image node_id 2 for calling a global function with example usage: test_is_singleton() without return types